ATL: ROSE - Advisories

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ATL: ROSE - Advisories

#1 Postby Subtrop » Sun Sep 19, 2021 4:01 am

WTNT32 KNHC 190836
TCPAT2

BULLETIN
Tropical Depression Seventeen Advisory Number 1
NWS National Hurricane Center Miami FL AL172021
800 AM CVT Sun Sep 19 2021

...NEW TROPICAL DEPRESSION FORMS OVER THE FAR EASTERN TROPICAL
ATLANTIC...


SUMMARY OF 800 AM CVT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...11.8N 28.2W
ABOUT 330 MI...530 KM SW OF THE SOUTHERNMOST CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 800 AM CVT (0900 UTC), the center of newly formed Tropical
Depression Seventeen was located near latitude 11.8 North, longitude
28.2 West. The depression is moving toward the north-northwest near
14 mph (22 km/h), and this general motion is expected to continue
today. A motion toward northwest is forecast to begin by tonight
and continue through Tuesday.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Some strengthening is expected for the next couple of days, and the
depression could become a tropical storm later today or on Monday.
By Tuesday, environmental conditions are is expected to become less
conducive for development, and the system is forecast to begin a
slow weakening trend.

The estimated minimum central pressure is 1007 mb (29.74 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
Next complete advisory at 200 PM CVT.

$$
Forecaster Stewart

WTNT42 KNHC 190859
TCDAT2

Tropical Depression Seventeen Discussion Number 1
NWS National Hurricane Center Miami FL AL172021
800 AM CVT Sun Sep 19 2021

The small low pressure system that the NHC has been tracking the
past few days has acquired a well-defined circulation and enough
organized deep convection to be classified as a tropical depression.
The initial intensity of 30 kt is based on 0000 UTC ASCAT wind data
of about 30 kt. This intensity is also supported by consensus Dvorak
satellite classifications of T2.0/30 kt from TAFB and SAB.

The initial motion estimate is north-northwestward or 330/12 kt.
The small cyclone is forecast to move in a general northwestward
direction throughout the remainder of the forecast period as the
system moves along the southwestern and western periphery of a
subtropical ridge that extends westward from Africa across the Cabo
Verde Islands. The NHC forecast track lies down the middle of the
tightly packed track models.

Only modest strengthening is expected during the next 48 hour so
while the small cyclone remains over 27-28 deg C sea-surface
temperatures and the vertical wind shear decreases to near 5 kt
during that time. However, proximity to dry air is expected
prevent any significant strengthening from occurring. By late
Tuesday, a slow weakening trend is forecast to begin as the system
moves over cooler water and the shear increases from the southwest.
The NHC intensity forecast closely follows a blend of the IVCN and
HCCA intensity consensus models through 72 hours, and then is lower
than the HCCA model on days 4 and 5.

FORECAST POSITIONS AND MAX WINDS

INIT 19/0900Z 11.8N 28.2W 30 KT 35 MPH
12H 19/1800Z 13.4N 29.2W 35 KT 40 MPH
24H 20/0600Z 15.5N 31.2W 40 KT 45 MPH
36H 20/1800Z 17.6N 33.2W 40 KT 45 MPH
48H 21/0600Z 19.7N 34.7W 35 KT 40 MPH
60H 21/1800Z 21.7N 36.1W 35 KT 40 MPH
72H 22/0600Z 23.2N 37.2W 30 KT 35 MPH
96H 23/0600Z 25.6N 39.6W 30 KT 35 MPH
120H 24/0600Z 28.1N 41.5W 30 KT 35 MPH

$$
Forecaster Stewart
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Re: ATL: SEVENTEEN - Advisories

#2 Postby cycloneye » Sun Sep 19, 2021 11:44 am

Tropical Depression Seventeen Discussion Number 2
NWS National Hurricane Center Miami FL AL172021
200 PM CVT Sun Sep 19 2021

The low-level center of the depression was exposed on visible
satellite imagery this morning but recently a new burst has formed.
Since the morning scatterometer passes missed the depression, the
intensity is held at 30 kt based on consensus T-2.0 values from TAFB
and SAB.

The initial motion estimate is 330/12. The cyclone is forecast to
move in a general northwestward direction throughout the remainder
of the forecast period as the system moves along the southwestern
and western periphery of a subtropical ridge that extends westward
from Africa across the Cabo Verde Islands. No significant changes
were made to the previous NHC forecast track, and the new
prediction lies near the middle of the tightly clustered track
models.

Environmental conditions are conducive for strengthening during the
next day or so, with wind shear forecast to drop off later today.
Thus, the official forecast calls for strengthening during the next
24 hours, and is close to the lower half of the intensity guidance
envelope, near the weaker global models. This forecast could be
conservative, since SSTs will be near 27C and mid-level atmospheric
moisture will be enough to support intensification. By 36-48 hours,
the southwesterly shear will increase, which should end the
opportunity for strengthening, and will likely cause slow weakening.
The models hold onto this system through the 5 day period, but it is
possible that the cyclone could become a remnant low in 4-5 days if
the shear is too much for the system to handle.


FORECAST POSITIONS AND MAX WINDS

INIT 19/1500Z 13.2N 28.8W 30 KT 35 MPH
12H 20/0000Z 14.7N 30.1W 35 KT 40 MPH
24H 20/1200Z 16.7N 32.2W 40 KT 45 MPH
36H 21/0000Z 18.9N 33.9W 40 KT 45 MPH
48H 21/1200Z 21.0N 35.4W 35 KT 40 MPH
60H 22/0000Z 22.7N 36.5W 35 KT 40 MPH
72H 22/1200Z 24.0N 37.6W 35 KT 40 MPH
96H 23/1200Z 26.3N 39.9W 30 KT 35 MPH
120H 24/1200Z 28.3N 41.2W 30 KT 35 MPH

$$
Forecaster Hagen/Blake
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Re: ATL: ROSE - Advisories

#3 Postby cycloneye » Sun Sep 19, 2021 3:40 pm

BULLETIN
Tropical Storm Rose Advisory Number 3
NWS National Hurricane Center Miami FL AL172021
800 PM CVT Sun Sep 19 2021

...ROSE BECOMES THE SEVENTEENTH NAMED STORM OF THE BUSY 2021
HURRICANE SEASON...


SUMMARY OF 800 PM CVT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...14.3N 29.9W
ABOUT 370 MI...595 KM W OF THE SOUTHERNMOST CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 800 PM CVT (2100 UTC), the center of Tropical Storm Rose was
located near latitude 14.3 North, longitude 29.9 West. Rose is
moving toward the north-northwest near 16 mph (26 km/h). A motion
toward the northwest is forecast to begin by tonight and continue
through Wednesday.

Maximum sustained winds have increased to near 40 mph (65 km/h)
with higher gusts. Some strengthening is expected through Monday.
By Tuesday, environmental conditions are expected to become less
conducive, and Rose is forecast to begin a slow weakening trend.

Tropical-storm-force winds extend outward up to 35 miles (55 km)
from the center.

The estimated minimum central pressure is 1005 mb (29.68 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
Next complete advisory at 200 AM CVT.

$$
Forecaster Hagen/Blake


Tropical Storm Rose Discussion Number 3
NWS National Hurricane Center Miami FL AL172021
800 PM CVT Sun Sep 19 2021

Satellite images show that deep convection has increased in
coverage near the low-level center during the last 6 hours, while
the overall structure of the tropical cyclone has also improved.
Based on the improved organization and consensus T-2.5 numbers from
TAFB and SAB, the initial intensity is set to 35 kt, making Rose
the seventeenth named storm of the busy 2021 Atlantic hurricane
season. Only 2005 and 2020 have had the seventeenth named storm on
an earlier date.

The 12-hour motion is north-northwest, or 330/14. However, Rose
appears to be moving more in a northwest direction during the past
few hours. This is probably the start of a northwest motion
that should continue through day 4 as the system moves along the
southwestern and western periphery of a subtropical ridge that
extends from Africa across the Cabo Verde Islands. A turn to the
north is predicted in about 5 days, as Rose comes under the
influence of a strong mid-level trough approaching from the
northwest. No significant changes were made to the previous track
forecast.

Environmental conditions are conducive for strengthening during the
next day or so, with low wind shear, SSTs near 27C, and sufficient
mid-level atmospheric moisture. Therefore, a little more
strengthening is shown compared to the previous NHC forecast. The
new NHC forecast is in agreement with the various consensus aids,
but slightly below the SHIPS model, in deference to the global
models which show a weaker cyclone. Westerly wind shear will
likely increase in about 36 hours as a strong upper-level trough
approaches from the northwest. Given that the cyclone is forecast
to remain rather small, it will likely be vulnerable to the higher
shear so weakening is forecast in the 36-72 h time period. Beyond
day 3, a further increase in wind shear is expected to cause Rose to
weaken to a tropical depression. Although not explicitly forecast,
it is possible that the cyclone could become a remnant low in 4-5
days if the shear is too much for the system to handle.


FORECAST POSITIONS AND MAX WINDS

INIT 19/2100Z 14.3N 29.9W 35 KT 40 MPH
12H 20/0600Z 15.9N 31.4W 40 KT 45 MPH
24H 20/1800Z 17.9N 33.3W 45 KT 50 MPH
36H 21/0600Z 20.0N 34.8W 45 KT 50 MPH
48H 21/1800Z 22.0N 36.0W 40 KT 45 MPH
60H 22/0600Z 23.5N 37.0W 40 KT 45 MPH
72H 22/1800Z 24.7N 38.0W 35 KT 40 MPH
96H 23/1800Z 26.7N 40.6W 30 KT 35 MPH
120H 24/1800Z 28.7N 41.2W 30 KT 35 MPH

$$
Forecaster Hagen/Blake
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Re: ATL: ROSE - Advisories

#4 Postby cycloneye » Sun Sep 19, 2021 10:00 pm

Tropical Storm Rose Discussion Number 4
NWS National Hurricane Center Miami FL AL172021
1100 PM AST Sun Sep 19 2021

The center of Rose has been very difficult to locate in infrared
satellite imagery this evening. However, an earlier ASCAT-A overpass
as well as an SSMIS microwave image from around of the time of the
previous advisory were both helpful in establishing the initial
position, motion, and intensity of the tropical cyclone. Rose's
center is located on the eastern edge of the main convective mass
due to some southeasterly shear. The ASCAT ambiguity data revealed
an area of 30-35 kt winds around the southeastern portion of the
circulation, so the wind speed remains 35 kt for this advisory.
This is also in agreement with subjective Dvorak T-numbers of T2.5
form both SAB and TAFB.

The ASCAT data indicated that Rose is located slightly west of the
earlier estimates, and the initial motion estimate is now
northwestward or 320/14 kt. The cyclone is forecast to move
generally northwestward during the next several days around the
southwestern and western portions of a subtropical ridge located
over the far eastern Atlantic. After day 4, a strong mid- to
upper-level trough over the north-central Atlantic should cause
Rose to turn northward. The dynamical models are in reasonably
good agreement through about 60-72 hours, but there is growing
east-to-west (cross-track) spread after that time. The NHC track
forecast is not too different from the previous advisory, and lies
close to the various consensus models in deference to the
increasing model spread late in the period.

Rose has about 24 hours over warm waters and in low vertical wind
shear conditions in which to strengthen, and the new NHC intensity
forecast for that time is unchanged from before. After 24 hours,
increasing westerly shear is likely to result in some gradual
weakening. A further increase in shear is anticipated by day 3 as
Rose approaches the aforementioned trough. This is likely to result
in additional weakening, and Rose is forecast to weaken to a
tropical depression by day 4. Some of the global model guidance
suggests that weakening could occur faster than indicated below, and
it is possible that Rose will degenerate into a remnant low by the
end of the forecast period.


FORECAST POSITIONS AND MAX WINDS

INIT 20/0300Z 15.3N 31.1W 35 KT 40 MPH
12H 20/1200Z 16.9N 32.6W 40 KT 45 MPH
24H 21/0000Z 18.9N 34.2W 45 KT 50 MPH
36H 21/1200Z 20.9N 35.5W 40 KT 45 MPH
48H 22/0000Z 22.6N 36.6W 40 KT 45 MPH
60H 22/1200Z 23.9N 37.5W 40 KT 45 MPH
72H 23/0000Z 25.0N 38.7W 35 KT 40 MPH
96H 24/0000Z 27.1N 40.8W 30 KT 35 MPH
120H 25/0000Z 29.0N 40.5W 30 KT 35 MPH

$$
Forecaster Brown
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Re: ATL: ROSE - Advisories

#5 Postby cycloneye » Mon Sep 20, 2021 4:00 am

Tropical Storm Rose Advisory Number 5
NWS National Hurricane Center Miami FL AL172021
500 AM AST Mon Sep 20 2021

...ROSE CONTINUES MOVING NORTHWESTWARD OVER THE EASTERN TROPICAL
ATLANTIC WITH NO CHANGE IN STRENGTH...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...15.9N 32.6W
ABOUT 550 MI...885 KM W OF THE SOUTHERNMOST CABO VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 500 AM AST (0900 UTC), the center of Tropical Storm Rose was
located near latitude 15.9 North, longitude 32.6 West. Rose is
moving toward the northwest near 15 mph (24 km/h), and this motion
at a slightly slower forward speed is forecast over the next few
days.

Maximum sustained winds are near 40 mph (65 km/h) with higher gusts.
Slight strengthening will be possible today. By Tuesday, however,
upper-level winds are expected to become less conducive, and Rose is
forecast to begin a slow weakening trend.

Tropical-storm-force winds extend outward up to 35 miles (55 km)
from the center.

The estimated minimum central pressure is 1005 mb (29.68 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
Next complete advisory at 1100 AM AST.

$$
Forecaster Stewart
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Re: ATL: ROSE - Advisories

#6 Postby cycloneye » Mon Sep 20, 2021 9:51 am

Tropical Storm Rose Discussion Number 6
NWS National Hurricane Center Miami FL AL172021
1100 AM AST Mon Sep 20 2021

While a cursory look at visible satellite images would suggest Rose
is intensifying, other data show that it remains a sheared storm.
The low- and mid-level centers remain roughly 90 n mi apart
according to SSMIS microwave, and a 1038Z ASCAT-A scatterometer
pass showed no significant change in intensity overnight. The
current wind speed is kept at 35 kt, with a much heavier weight on
the 30-kt scatterometer pass than Dvorak estimates near 55 kt. This
is a good example of the value of the scatterometer which can tell
the forecaster much more about the surface winds that conventional
satellite estimates can miss (even if the data is possibly too low
with all the thunderstorm activity).

There are a lot of thorns in the way of Rose blossoming into a
stronger storm. Increasing shear and drier mid-level air are on
the way for tonight, competing against the somewhat warm SSTs.
Thus Rose has about a day to flower into a moderate tropical storm,
and no significant change was made to the short term forecast. At
longer range, stronger shear and dry air should pull the petals off
Rose one-by-one, causing the cyclone to slowly weaken. The new
forecast is similar to the previous one, with some small 5-kt
downward adjustments. Rose could even shrivel up into a remnant
low by day 5, but that's not shown yet in the forecast.

The initial motion remains northwestward at about 14 kt. Rose is
still expected to move generally northwestward around the
southwestern and western periphery of a strong subtropical ridge
during the next few days. Around day 3, however, a mid- to
upper-level trough over the north-central Atlantic is forecast to
dig southeastward, causing the cyclone to turn northward and
eventually northeastward by the weekend. Guidance is in much
better agreement on this scenario than the last cycle (though
there are still some westward model solutions), and the new NHC
track forecast is shifted northeastward at long range.


FORECAST POSITIONS AND MAX WINDS

INIT 20/1500Z 17.3N 33.4W 35 KT 40 MPH
12H 21/0000Z 19.0N 34.8W 40 KT 45 MPH
24H 21/1200Z 21.0N 36.1W 35 KT 40 MPH
36H 22/0000Z 22.6N 37.1W 35 KT 40 MPH
48H 22/1200Z 24.1N 38.1W 35 KT 40 MPH
60H 23/0000Z 25.4N 39.1W 30 KT 35 MPH
72H 23/1200Z 26.7N 40.0W 30 KT 35 MPH
96H 24/1200Z 29.0N 40.0W 25 KT 30 MPH
120H 25/1200Z 31.0N 38.0W 25 KT 30 MPH

$$
Forecaster Blake
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